# Variable Parameters

Variable Parameters — MC Grating documentation for Modal Crossed and Chandezon Crossed. A checked box means that the corresponding parameter (Wavelength,…

Canonical: https://mcgrating.com/docs/common-crossed/variable.html


Written by Nikolay M. LyndinLast revised 2013-10-16

This documentation was written for releases up to 2018 and is being revised. Some dialogs have changed since. If something does not match what you see, write to [mc@mcgrating.com](mailto:mc@mcgrating.com).

A checked box means that the corresponding parameter (*Wavelength, Period, Normal Angle *and *Plane Angle *will be varied to optimize the ***[Criterion Function](https://mcgrating.com/docs/common-crossed/criterion.html)***. It also means that the user can edit the above variables as the starting optimization parameters. If a box is not checked these edit controls are inactive and display the current *criterion point arguments* values during the optimization. The above parameters can be set as variable only if the *Criterion function* has the same parameter value for all *Criterion points*.
 The user can check the structure parameters under optimization by way of ***Settings Dialog*** after the ***Export*** procedure.

The structure layers with identical refractive indexes can be combined in a group identified by its index number by selecting the check box in the *Material Group* control. If the *Add To Group *of the *Material Group* control is selected, the *Group* control indicates the index of group which corresponds to the selected Layer while the *Members* control indicates total number of elements in the current group. The maximum allowed *Group Index* always corresponds to an empty group; it automatically increases or decreases as soon as a first refractive index group member is introduced or the last refractive index group member is removed. If the *Set group Parameters *of the *Material Group* control is selected, the refractive index of the selected group and its variable status can be set while the *Member* control allows inspecting of current group member other parameters. After start the *Optimization* all material assignment for media in the group will be removed.

**Note 1 **The checked box ***X-p/Y-p=const*** imposes constrain on periods ratio. This constrain is also valid for Criterion points.
 **Note 2 **During the ***[Optimization](https://mcgrating.com/docs/common/optimization.html)*** process the edit controls are disabled but they display every second the real time values. In addition, if the user changes the *Group Index*, *Layer Index* or *Interface Index* the related parameters will be updated immediately.

From the in-application help of Modal Crossed, documented through 2018. If you publish results computed with MC Grating, see [how to cite it](https://mcgrating.com/references.html#cite).